X-Ray Security Inspection Machine

ABSTRACT

X-ray security inspection machine ( 10 ) comprising an X-ray tunnel ( 40 ); a conveyor means ( 50 ) for conveying an article through the tunnel; an X-ray source for irradiating the article; and an X-ray detection means for detecting X-rays transmitted through the article. In one aspect, the detection means comprises a photodetector array module ( 20 ) actuatable between a first stowed configuration and a second deployed configuration. In a second aspect, the detection means comprises a first unit having a first photodetector array ( 22 ); and a second unit, having a second photodetector array ( 24 ), offset with respect to the first unit. The units are moveable relative to one another between a first arrangement where the arrays overlap to a first degree and a second arrangement where they overlap to a second, lower degree; preferably zero. Also, a conveyor belt-tracking device ( 100 ) comprising a guide frame ( 104 ) to receive the conveyor belt ( 116 ) and substantially to restrict its motion to a predetermined direction.

The invention relates to an X-ray security inspection machine, inparticular an X-ray security inspection machine having a compactprofile.

X-ray security inspection machines are widely used at securitycheckpoints, such as those in airports, courthouses, government offices,embassies, schools and prisons. Where space is not restricted or wherean X-ray security inspection machine is required on a permanent basis,the machine may be set up and configured on site, and retained thereindefinitely. Such machines are provided in various sizes andspecifications, depending on their intended application. FIG. 1 shows aperspective view of such a prior art X-ray security inspection machine1, manufactured as model 520B by Rapiscan Security Products Ltd, of WestSussex, United Kingdom (Rapiscan). The machine, 1 has a standard tunnelopening 2 of 640 mm wide by 430 mm high to accommodate relatively largeluggage and package sizes. The overall dimensions of the machine 1 are2570 mm long by 1345 mm high by 835 mm wide, which is actually at themore compact end of the range for permanent machines, many of which aresignificantly larger.

Nevertheless, as the issue of security becomes an ever greater priority,there is an increasing demand for X-ray security inspection machineswhich find more widespread application. In particular, there is a needfor X-ray security inspection machines which may be employed inspace-restricted environments and/or which are readily moveable, i.e.portable, from one location to another. X-ray security inspectionmachines, such as machine 1 above, suffer from a number of problems inthis respect. Firstly, this type of machine is heavy, bulky and notreadily portable. Secondly, the machine is too wide to be able to passthrough a standard doorway, of width 765 mm, without first beingdisassembled. Thirdly, a skilled service technician is required to takethe machine apart at its original location and to re-assemble it at itsfinal location, which is both costly and time-consuming.

FIG. 2 shows a perspective view of another prior art X-ray securityinspection machine 5, also manufactured by Rapiscan, as model 520S. Themachine 5 is provided with castors 6 and a fold-up conveyor 7, which,combined with a narrow overall width of 735 mm, enables ease of movementin many situations where a full-size X-ray machine cannot be deployed.The machine 5 has overall dimensions of 2480 mm long by 1170 mm high by735 mm wide. However, although the machine 5 is narrow and capable ofpassing through a standard doorway, the machine suffers from the problemof having a tunnel opening 8 of only 550 mm wide by 360 mm high.Compared with the standard tunnel opening 2 of 640 mm wide by 430 mmhigh, then, the machine 5 is not able to accommodate such large luggageand package sizes and is therefore of limited application.

There is a need, therefore, for an improved X-ray security inspectionmachine which may be employed in space-restricted environments and/orwhich is readily moveable, i.e. portable, from one location to another.It would be desirable for such a machine to be moveable without the needfor a skilled service technician. It would also be desirable for such amachine to be portable without the need for disassembly. In particular,it would be desirable for such a machine to be capable of passingthrough a standard doorway. Furthermore, it would be desirable for sucha machine to provide a tunnel opening of standard dimensions, namely of640 mm wide by 430 mm high.

The invention aims to address the above and other objectives byproviding an improved X-ray security inspection machine.

According to one aspect of the invention, there is provided an X-raysecurity inspection machine, comprising: an X-ray tunnel for receivingan article to be inspected; a conveyor means for conveying the articlethrough the tunnel; an X-ray source for irradiating the article withinthe tunnel; and an X-ray detection means for detecting X-raystransmitted through the article, wherein the X-ray detection meanscomprises a photodetector array module actuatable between a first stowedconfiguration and a second deployed configuration.

The provision of a photodetector array module which may be moved betweena stowed configuration and a deployed configuration has the advantage ofreducing the width of the machine when not in use, thereby facilitatingmovement of the machine between locations of use, especially inspace-restricted environments. What is more, because the photodetectorarray module may be actuated to a deployed, operational position, thedimensions of the tunnel opening of the machine are to some extentindependent of the overall width of the machine when configured forrelocation. For previous X-ray security inspection machines, the overallwidth of the machines is a function of the tunnel opening width and thewidth of the housing which surrounds the opening, containing control anddetection electronics, power and control cables, and X-ray shieldingmaterial etc. The photodetector arrays of these machines are fixedassemblies on the general housing frameworks of the machines. Thus ithas been commonly held that, in order to provide a machine width of lessthan a standard doorway (765 mm), a correspondingly smaller tunnelopening is necessary. In particular, it has not been possible previouslyto achieve an X-ray security inspection machine having a standard tunnelopening of 640 mm by 430 mm while also having a width of less 765 mm,preferably having a width of 735 mm.

By providing a photodetector array module which may be movedindependently with respect to the machine, when the module is in itsstowed position, those parts of the module which contribute to itswidth—namely electronics, cables and shielding material—may be storedwithin the overall profile of the machine, occupying a region of thetunnel itself. Preferably, in this configuration, the photodetectorarray module is substantially flush with the X-ray machine housing. Inthe stowed configuration, then, the tunnel opening has a reduced size atthe location of the photodetector array module. Upon actuation of themodule to its deployed configuration, the module is translated away fromthe tunnel to project from the machine housing, thereby clearing thetunnel opening to its standard dimensions ready for use.

The X-ray security inspection machine of the invention may therefore beemployed in space-restricted environments. Furthermore, the machine isreadily moveable, i.e., portable, from one location to another. Sincethe photodetector array module is stowable to provide a compact profileto the machine, which may therefore be readily moved, neitherdisassembly nor the services of a skilled engineer is required to movethe machine. In certain embodiments, the machine has the particularadvantage of being capable of providing a tunnel opening of standarddimension, namely of 640 mm wide by 430 mm high, while still being ableto be passed through a standard doorway, of 765 mm width. A user of theX-ray inspection security inspection machine may therefore move themachine quickly and easily and configure the machine at its new locationwith minimal setting up time. The machine may therefore find readyapplication at smaller installations, where space is at a premium, suchas in schools, prisons, offices and other areas where it is difficult toinstall a conventional X-ray facility.

Preferably, the photodetector array module is actuatable by a linearactuation means coupled to the module. Preferably, the actuation meansemploys a linear guide rail to define the direction of motion of thephotodetector array module, so that its movement between stowed anddeployed configurations is consistently reproducible.

Preferably, the photodetector array module comprises two substantiallyperpendicular photodetector arrays, in an “L”-shaped arrangement, one ofthe arrays being disposed across a top region of the tunnel and theother array being disposed across a side region of the tunnel.Preferably, the X-ray detection area provided by the first photodetectorarray is supplemented by a further photodetector array, which isprovided adjacent the first array, on the opposite side from the secondarray, and is positioned in fixed relation to the X-ray machine. Thestationary photodetector array is preferably positioned at a verticallyhigher level than the first photodetector array, so that when thephotodetector array module is retracted to its stowed configuration, apart of the first photodetector array slides under the stationaryphotodetector array, the two arrays then at least partially overlapping.This has the advantage of providing a relatively large anduninterrupted/continuous X-ray detection area at the upper region of thetunnel in the deployed configuration, but because of the two-part,overlapping arrangement of the stationary and first photodetector arraysin the stowed configuration, the width of the photodetector array moduleitself is smaller than the overall X-ray detection width of the X-raydetection means, providing the advantages discussed above.

Preferably, the substantially uninterrupted X-ray detection area equalsthe overall X-ray detection area provided by the X-ray detection meansin the first substantially planar extent.

Preferably, the photodetector array module is translated betweenapproximately 60 mm to 100 mm, but particularly 80 mm, between thestowed configuration and the deployed configuration of the module.

Preferably, a control console for controlling operation of the X-raysecurity inspection machine is also stowable into the machines housing.Preferably still, deployment of the control console is performedautomatically with actuation of the photodetector array module. In thisway, activation of the machine quickly deploys the machine to itsconfiguration ready for use.

According to a further aspect of the invention, there is provided aconveyor belt-tracking device for tracking a conveyor belt of an X-raysecurity inspection machine in a straight line, the device comprising aguide frame arranged to receive the conveyor belt and substantially torestrict motion of the conveyor belt to a predetermined direction.

A problem with conveyor belt systems is that the conveyor belt tends totrack off centre, which can result in damage to the machine in two ways.Firstly, the conveyor belt itself can become worn and need replacing.Secondly, the belt can cut through cables inside the machine, which isboth dangerous and may prevent operation of the machine altogether. Theprovision of a guide frame which receives the conveyor belt andconstrains its motion to a predetermined direction provides theadvantage of keeping the belt tracked in a straight line, so that it maynot move away from this line.

Preferably, the guide frame has upper and lower runner portions betweenwhich the conveyor belt slides, so that movement of the conveyor belt inall directions perpendicular to the predetermined direction may besubstantially prevented.

According to a further aspect of the present invention, there isprovided an X-ray security inspection machine, comprising: an X-raytunnel for receiving an article to be inspected; a conveyor means forconveying the article through the tunnel; an X-ray source forirradiating the article within the tunnel; and an X-ray detection meansfor detecting X-rays transmitted through the article, the X-raydetection means comprising: a first unit having a first photodetectorarray; and a second unit having a second photodetector array and beingoffset with respect to the first unit, wherein the first and secondunits are moveable relative to one another between a first arrangementin which the first and second photodetector arrays overlap to a firstdegree and a second arrangement in which the first and secondphotodetector arrays overlap to a second, lower degree.

The provision of a two-part X-ray detection means, with the two unitsbeing offset with respect to and moveable relative to one another,allows the X-ray detection area of the X-ray detection means to bevaried, according to the degree of overlap of the units. A maximumcontinuous X-ray detection area is provided when the two photodetectorarrays have zero degree of overlap, but are adjacent one another (sothat projections of their individual X-ray detection areas onto the sameprojection plane would adjoin one another). A greater degree of overlapwill reduce the continuous X-ray detection area. When the twophotodetector arrays fully overlap, i.e. when one unit is fully obscuredby the other unit, only the unobscured unit is used for X-ray detection.

Of course, when the two units overlap, the width of the X-ray detectionmeans is reduced. In this way, the same advantages discussed above areachievable, since the units may be arranged to overlap when the machineis not in use—thereby providing a more compact machine profile formanoeuvrability in confined areas—and to move apart from each other toreduce the degree of overlap when set up for use—thereby providing anX-ray detection area and corresponding tunnel size of greater size,particularly of the standard dimensions specified above.

Other preferred features and advantages of the invention are set out inthe description and in the dependent claims which are appended hereto.

The invention may be put into practice in a number of ways and someembodiments will now be described, by way of non-limiting example only,with reference to the following figures, in which:

FIG. 1 shows a perspective view of a prior art X-ray security inspectionmachine, intended for substantially permanent installation;

FIG. 2 shows a perspective view of a prior art portable X-ray securityinspection machine;

FIG. 3 shows a perspective view of an X-ray security inspection machineaccording to a first embodiment of the invention, in which the machineis deployed for use;

FIG. 4 shows a perspective view of the embodiment of FIG. 3, in whichthe machine is in its stowed configuration ready to be moved;

FIG. 5 shows a perspective view of an X-ray security inspection machineaccording to a second embodiment of the invention, in which the machineis in its stowed configuration;

FIG. 6 shows a perspective view of the embodiment of FIG. 5, at anintermediate stage of deployment for use;

FIG. 7 shows a perspective view of the embodiment of FIG. 5, in whichthe machine is deployed for use;

FIG. 8 shows a perspective view of a photodetector array unit accordingto an embodiment of the invention;

FIG. 9 shows a perspective view of a belt-tracking device in accordancewith an embodiment of the invention;

FIG. 10 shows a perspective view of the belt-tracking device inaccordance with a further embodiment of the invention; and

FIG. 11 shows a side sectional view of a conveyor and the belt-trackingdevice in accordance with a still further embodiment of the invention.

Referring to FIG. 3, there is shown an X-ray security inspection machine10 in accordance with a first embodiment of the invention. In thisembodiment, the machine is fully deployed ready for use. A photodetectorarray module 20 has been extended to its deployed position and projectsfrom the X-ray machine's housing 30. The extent of projection of thephotodetector array module 20 is typically between 60 mm and 100 mm, butpreferably the module extends by approximately 80 mm from the housing.

Contained within the housing 30 are the necessary components forproviding an X-ray security inspection machine, including an X-raygenerator, processing and control electronics, power and control cables,a computer processor and memory storing suitable operational software,and X-ray shielding material, as will be understood by the skilledperson.

Above the X-ray generator (not shown) within the housing 30 and belowthe upper surface of the photodetector array module 20, the housingdefines a tunnel 40, having a substantially rectangular tunnel opening41. Items to undergo X-ray inspection in the machine 10 pass through thetunnel 40 for irradiation by X-ray photons. Those photons which aretransmitted through the item under inspection are then detected. Thetunnel opening 41 has standard dimensions of 640 mm wide by 430 mm high,in this embodiment.

The tunnel 40 passes through the housing 30 from an input side 42 to anoutput side 43. In order to help define a maximum item size which may beinspected with the machine 10, a respective plurality of tunnel wallpanels 44, 45 are disposed around the tunnel openings at the input andoutput sides 42, 43. The panels are preferably made of a transparentplastics material, such as polycarbonate, Plexiglas™ or Perspext™, tofacilitate observation of items passing into and out of the tunnel 40.

A conveyor system 50 transports items for inspection from the input side42 of the tunnel 40 to its output side 43. In the embodiment shown inFIG. 3, the conveyor system 50 comprises three separate conveyors: aninput conveyor 51 having an associated conveyor belt 52; an outputconveyor 53 having an associated conveyor belt 54; and an intermediateconveyor (not shown) located within the tunnel 40 and having its ownassociated conveyor belt (also not shown). Other arrangements of theconveyor system will be readily apparent to the skilled person.

The X-ray security inspection machine 10 incorporates a control console60, comprising a monitor 62 and a keypad/mouse pad 64, by means of whichan operator may control the machine. The control console 60 is stowable,so that it does not contribute to the overall width of the machine 10,when in its stowed configuration.

Initial activation and subsequent deactivation of the machine 10 areachieved by means of activation control switches 66, which areaccommodated on the housing 30, preferably not on either lateral sidesof the machine, so as not to increase the width profile of the machine.The activation controls 66 may include a key switch to ensure operationonly by authorised personnel, or the like.

The X-ray security inspection machine 10 is provided with a set ofwheels or castors 70, on which the machine is supported and by means ofwhich the machine may be moved. The wheels 70 may be standard nylonwheels, conventionally used. However, nylon wheels tend to be relativelyhard which makes movement of the machine over certain surfaces,especially uneven surfaces, somewhat difficult. Preferably, the wheelsare provided by rubber castors, which are capable of conforming morereadily to surface unevenness and reducing the impact on the machinewhen encountering such surfaces. This specification of wheel alsoreduces vibration of the machine during transportation. In order tofacilitate such movement, a steering and braking handle 72 is provided.The steering and braking handle 72 co-operates with the wheels 70, atleast to provide a braking mechanism if not also to provide a steeringmechanism for changing direction of the machine. In the deployedconfiguration of the machine 10 ready for use, the steering and brakinghandle 72 is itself stowed away beneath the machine, as shown in FIG. 3.

FIG. 4 shows the embodiment of FIG. 3 when the machine 10 is in itsstowed configuration, ready to be moved from one location to another.The photodetector array module 20 has been retracted towards the tunnel40, so that its outer surface is substantially flush with the machinehousing 30. The control console 60 has also been stowed away, thekeypad/mouse pad 64 having been dropped down and translated towards thecentre of the machine, and the monitor 62 having been folded down overthe keypad/mouse pad to lie substantially flush with the surroundinghousing 30. In particular, retraction of the keypad/mouse pad 64 intothe housing 30 means that the width of the machine 10 is substantiallythat of the housing itself and is not increased by the photodetectorarray module 20 or control console 60.

The tunnel wall panels 44, 45 are foldable panels, such that thegenerally vertical panels (in the deployed configuration) fold onto thegenerally horizontal panel, which itself folds down towards the tunnelopening 41 at its respective input or output side 42, 43. The input andoutput conveyors 51, 53 are also hingedly attached to the machinehousing 30, such that they may be folded upwards to cover the tunnelopening 41, in their stowed positions.

Finally, the steering and braking handle 72 has been drawn out from itsstowed position under the machine 10, to assist the movement of themachine. The handle 72 cooperates with a braking mechanism via a lever,which in FIG. 4 has been released, to permit free rotation of the wheels70. The steering handle 72 may be a simple couple to the machine 10 forpushing or pulling the machine from one location to another.Alternatively, the handle 72 may be coupled to a pivoting wheel assembly(not shown), to facilitate changes of direction when the machine ismoved.

Once the machine 10 is wheeled to a desired location, the brakeassociated with the steering and braking handle 72 is applied and thehandle is stowed away into the housing 30 at the bottom of the machine.Next, the input and output conveyors 51, 53 are folded down to asubstantially horizontal orientation. The tunnel wall panels 44, 45 arefolded out around the tunnel opening 41 on either side. The monitor 62,which is preferably a LCD monitor, is provided with a quick-releaselatching mechanism, so that once pressed down, the control console 60opens out. The monitor 62 opens up automatically and the keypad/mousepad 64 protrudes forward and is inclined, for use. The activationcontrol 66 is next operated, to turn the machine 10 on. Upon activation,the photodetector array module 20 is translated from its stowedconfiguration to its deployed configuration, protruding from the housing30 in its final operational position. During this sequence, themachine's control systems perform radiation checks and other standardsoftware checks, to ensure that the machine is operational. Followingthis procedure, the machine is ready for use.

FIGS. 5 to 7 illustrate the above sequence with reference to a secondembodiment of the invention. In FIG. 5, the machine 10 is in its stowedconfiguration suitable for transportation of the machine. In thisembodiment, the control console 60 is provided as a differentarrangement from the previous embodiment, and the screen 62 andkeypad/mouse pad 64 are not arranged to deploy automatically, nor inconcert. The monitor 62 is positioned on top of the housing 30 and isarranged to pivot between a stowed position, substantially parallel withthe top surface of the housing and an operational position,substantially normal to the upper surface of the housing. Thekeypad/mouse pad 64 is stowed in a storage compartment 32 spaced awayfrom the photodetector array module 20. As in the previous embodiment,the photodetector array module 20 is substantially flush with the sidesurface of the housing 30 when in the stowed configuration.

FIG. 6 shows the machine 10 at the stage where manual deployment ofvarious parts of the machine has been completed. In particular, theinput and output conveyors 51, 53 and their associated tunnel wallpanels 44, 45 have been folded out to their operational configuration.The monitor 62 has been pivoted upwards from its stowed position and thekeypad/mouse pad 64 has been drawn out from its storage compartment 32and is supported by a stand 65.

Up until this point, the machine 10 has not actually been switched on.Operation of the activation controls 66 is required to initialize themachine and to deploy the photodetector array module 20. Upon suchoperation, the photodetector array module 20 slides out from the housing30 to its operational configuration, as shown in FIG. 7. Followingdeployment of the module 20, the tunnel opening 41 is uniform along itslength, at the standard dimensions of 640 mm by 430 mm, in thisembodiment. The machine width in its stowed configuration (i.e., that ofthe housing 30) is approximately 750 mm, and the machine width in itsdeployed configuration (i.e., taking account of the extension of thephotodetector array module 20 and the keypad/mouse pad 64) isapproximately 855 mm.

FIG. 8 shows a perspective view of the photodetector array module 20,without its casing and without the surrounding housing 30 of the machine10. In this embodiment, the photodetector array module 20 comprises afirst photodetector array 22, which extends substantially in a firstplane, and a second photodetector array 24, which extends substantiallyin a second plane perpendicular to the first plane. Thus first andsecond photodetector arrays 22, 24 form an “L”-shaped photodetectorarray. In the embodiment shown in FIG. 8, the first and secondphotodetector arrays 22, 24 are provided by respective photodetectorarray boards 23, 25 fixed to corresponding board supports arrangedgenerally along the first and second planes.

In the preferred embodiment of the invention, the X-ray generator ofmachine 10 is oriented vertically upwards and produces a fan-shape X-raybeam, which scans items under inspection on the conveyor system 50, toproduce an image of the contents of the item on monitor 62. Successivesections of the item under inspection are exposed to the narrow linearX-ray beam as the conveyor system moves the item relative to the beam.X-ray photons which are transmitted through the item and reach thephotodetector arrays are then detected. The transmitted light pattern sodetected is characteristic of the item being scanned. As the transmittedlight is received by the array of photodetectors, the photodetectorsgenerate electrical signals in accordance with the intensity of thatreceived light. This may be achieved either directly, using photodiodessensitive to X-rays, or indirectly, by using an X-ray phosphor, orscintillator, arranged over photodiodes sensitive to light of thewavelength(s) generated by the scintillator. In either case, the outputsof the photodetectors are sampled in sequence to provide a series ofsignals in accordance with the light received by the photodetectors.These signals are converted to digital form and stored in a memory andmay also be transmitted to the monitor 62 via suitable video outputcircuits, so that an image representative of the item under inspectionmay be viewed.

As discussed above, the photodetector array module 20 is translatablebetween a stowed position, in which the second photodetector array 24 issubstantially contained within the tunnel opening 41, and a deployedposition, in which the tunnel opening is unobstructed and the secondphotodetector array projects beyond the outer side surface of themachine housing 30. In the embodiment of FIG. 8, the photodetector arraymodule 20 is actuatable by means of a linear actuator 80, having anextendable and retractable arm 81. The actuator arm 81 is pivotallyattached at one end to a freely pivoting arm 82. The other end of thepivoting arm 82 is pivotally attached to a bracket 83, itself fixed withrespect to the machine 10 via an upper surface of the tunnel 40. Thelinear actuator 80 is also held in fixed relation to the machine 10 viacorresponding bracket 84, which is fixed to an upper surface of thetunnel 40, on the other side of the photodetector array module 20 thanbracket 83.

Thus, actuation of linear actuator 80 to extend or retract the actuatorarm 81 causes the pivoting arm 82 to pivot about its joint with bracket83. The linear, translational component of the rotational motion of thepivoting arm 82 is transmitted to the photodetector array module 20 bymeans of a sliding couple 85 provided at the centre of the pivoting arm82, which extends across the first photodetector array 22. In thisembodiment, the sliding couple 85 is provided by a longitudinallyextending slot formed in the pivoting arm 82 and a co-operating pinformed on the upper surface of the photodetector array module 20 andextending through the slot. Rotational motion of the pivoting arm 82 isthereby transformed into linear, translational motion of thephotodetector array module 20, so that the module may be translated intoand out of the stowed position.

In order to ensure precision motion of the photodetector array module20, a guide rail and roller assembly 86 is provided. The guide rail isfixed to an upper surface of the tunnel 40 and the rollers are providedon the photodetector array module 20, co-operatively engaging with theguide rail so as to ensure smooth linear motion of the module 20.

By appropriate selection of the pivot point between pivoting arm 82 andbracket 83, and of sliding couple 85, translation displacement of thephotodetector array module 20 may be set within a predetermined distancerange. Such a range corresponds to a minimum and maximum extension ofthe actuator arm 81, from being extended from its fully retractedposition to its fully extended position by linear actuator 80. In thepresent embodiment, the desired translational displacement of thephotodetector array module 20 is approximately 80 mm. Being able toreproduce consistently this extension of the module 20 results in acorresponding reproducibility in the alignment of the photodetectorarrays.

Fixed in relation to the tunnel 40 and the machine 10 generally, is astationary, third photodetector array 90, provided on a thirdphotodetector board 91 and associated board support. The stationaryphotodetector array 90 is positioned adjacent the first photodetectorarray, at an opposite end to that of the second photodetector array 24,so that, upon actuation of the photodetector array module 20, the firstphotodetector array 22 moves towards or away from the stationaryphotodetector array 90.

The third photodetector array board 91 is positioned at a verticallydifferent level from the first photodetector array board 23 closest tothe third photodetector array. As such, when the first detector array 22is translated towards the third photodetector array 90, the two arraysdo not come into physical contact with each other. Instead, the firstpart of the first photodetector array 22 (i.e. the first photodetectorarray board 23) slides under the third photodetector array board 91, sothat the two at least partially overlap one another. In the deployedconfiguration, the photodetector array boards 23, 91 may partiallyoverlap to a lesser degree than in the stowed configuration, or may notoverlap at all.

In this way, in the deployed configuration, an X-ray detection arealying generally in the first plane is provided by a combination of thefirst photodetector array 22 and the stationary photodetector array 90;that is, the X-ray detection area provided by the first photodetectorarray 22 is smaller than the overall X-ray detection area provided bythe machine 10 in the generally first plane, since the stationary, thirdphotodetector array 90 supplements the first photodetector array. Themoveable first and second photodetector arrays 22, 24 and thestationary, third photodetector array 90 can be considered to formtogether a two-part photodetector array “box”.

Although the X-ray detection area generally in the first plane may beprovided with a predetermined width to accommodate a desired tunnelopening width, because of the separate, first and third photodetectorarrays which may move relative to one another and more importantlyoverlap, the overall width of the machine 10 when not in use isadvantageously reduced from that which has been conventionallyachievable with prior art machines.

FIGS. 9 and 10 show perspective views of a conveyor belt-tracking device100, which may be used to maintain the tracking of a conveyor belt in anX-ray security inspection machine, to prevent the belt from tracking offline and cutting cables and/or damaging the belt. The tracking device100 includes a mounting bracket 102, for mounting the device to aconveyor system 50 and a guide frame 104 arranged to receive theconveyor belt and substantially to restrict the motion of the conveyorbelt to a predetermined direction, defined by the guide frame. In theembodiments shown in FIGS. 9 and 10, the guide frame comprises an upperand a lower runner portion 106, which overlie another and extend fromthe mounting bracket 102 to form generally rounded triangularprojections from the mounting bracket 102. The upper and lower runnerportions 106 are spaced apart from one another, so that a conveyor beltmay run between the two portions and not only prevent lateral movementof the conveyor belt away from the predetermined direction but also toprevent unwanted movement of the conveyor belt in substantially alldirections perpendicular to the predetermined direction.

FIG. 11 shows a side sectional view of a conveyor 110, having an idleroller 112 and a tracking roller 114, about which passes a conveyor belt116. The belt-tracking device 100 of the invention is mounted in thisembodiment between the idle and tracking rollers 112, 114, to receivethe conveyor belt 116 and to maintain its tracking. In anotherembodiment, two belt-tracking devices 100 may be positioned opposite oneanother on either side of the conveyor belt 116. In other embodiments,the belt-tracking device 100 may be located at any suitable positionalong the conveyor system, where tracking of the belt is desirable orneeded.

Preferably, the edges of the runner portions 106 are rounded off so asto reduce wear on the conveyor belt as a result of its interaction withthe belt-tracking device 100. The conveyor belt-tracking device 100 ofthe invention resolves the problem of the conveyor belt tracking offline and causing damage to an X-ray security inspection machine andthereby reduces maintenance costs for such a machine.

The invention has been described with reference to the above specificembodiments. However, the skilled person would readily appreciate thatfeatures of one embodiment may be equally incorporated into the otherembodiments. In addition, the skilled person will readily envisagealternatives, equivalents and modifications to the specific embodimentsdescribed above, which may be used to put the invention into practice.For example, the linear actuator 80 could be coupled to thephotodetector array module 20 without the use of the pivoting arm 82. Inaddition, two such linear actuators could be positioned on either sideof the photodetector array module 20 to provide the linear motion. Infact, any actuator capable of providing the desired translation of thephotodetector array module 20 could be used.

As to the control console 60, this may be deployed and retracted purelymanually, or by means of a quick release latching mechanism which, onceoperated, causes a substantially automatic deployment of the console.Alternatively, the control console 60 may be deployedelectromechanically. Such deployment may be by means of a mechanismcoupled to the photodetector array module actuator so that both thephotodetector array module and the control console are deployedtogether, automatically.

1-32. (canceled)
 33. An X-ray security inspection machine, comprising:an X-ray tunnel for receiving an article to be inspected; a conveyormeans for conveying the article through the tunnel; an X-ray source forirradiating the article within the tunnel; and an X-ray detection meansfor detecting X-rays transmitted through the article, wherein the X-raydetection means comprises a photodetector array module actuatablebetween a first stowed configuration and a second deployedconfiguration.
 34. The X-ray security inspection machine of claim 33,wherein when the photodetector array module is in its stowedconfiguration the photodetector array module occupies a region of theX-ray tunnel.
 35. The X-ray security inspection machine of claim 33,wherein when the photodetector array module is in its deployedconfiguration the X-ray tunnel is substantially unobstructed by thephotodetector array module.
 36. The X-ray security inspection machine ofclaim 33, wherein the machine comprises a housing and the photodetectorarray module in its stowed configuration is substantially flush with thehousing.
 37. The X-ray security inspection machine of claim 33, furthercomprising an actuation means for translating the photodetector arraymodule between the stowed and deployed configurations, wherein theactuation means comprises an extendable and retractable actuator armcoupled to the photodetector array module.
 38. The X-ray securityinspection machine of claim 37, wherein the actuator arm is coupled tothe photodetector array module via a pivoting arm extending across andslidingly coupled to the photodetector array module, such thatrotational movement of the pivoting arm effected by the actuator arm istransformed into translational movement of the photodetector arraymodule.
 39. The X-ray security inspection machine of claim 33, furthercomprising a guide for constraining the photodetector array module tolinear motion.
 40. The X-ray security inspection machine of claim 33,wherein the photodetector array module comprises a first photodetectorarray arranged to provide a first X-ray detection area having a firstsubstantially planar extent.
 41. The X-ray security inspection machineof claim 40, wherein the photodetector array module comprises a secondphotodetector array arranged to provide a second X-ray detection areahaving a second substantially planar extent perpendicular to the firstplanar extent.
 42. The X-ray security inspection machine of claim 40,wherein the first X-ray detection area provided by the photodetectorarray module is smaller than an overall X-ray detection area provided bythe X-ray detection means in the first substantially planar extent. 43.The X-ray security inspection machine of claim 40, the X-ray detectionmeans further comprising a stationary photodetector array which is fixedin relation to the X-ray tunnel and adjacent the photodetector arraymodule.
 44. The X-ray security inspection machine of claim 43, whereinthe stationary photodetector array is positioned in spaced relationshipwith respect to the first photodetector array, such that in the stowedconfiguration respective parts of the first and stationary photodetectorarrays overlap.
 45. The X-ray security inspection machine of claim 43,wherein when in the deployed configuration the first and stationaryphotodetector arrays provide a substantially continuous X-ray detectionarea.
 46. The X-ray security inspection machine of claim 33, wherein theX-ray tunnel has a tunnel opening of approximately 640 mm wide by 430 mmhigh.
 47. The X-ray security inspection machine of claim 33, wherein thephotodetector array module is translated by approximately 80 mm betweenthe first stowed configuration and the second deployed configuration.48. The X-ray security inspection machine of claim 33, wherein themachine has an overall width of less than approximately 765 mm, thewidth preferably being 735 mm.
 49. The X-ray security inspection machineof claim 33, further comprising a stowable control console, wherein thecontrol console is deployed automatically with the photodetector arraymodule, upon activation of the machine.
 50. The X-ray securityinspection machine of claim 33, wherein the X-ray tunnel has an inputopening and an output opening and the conveyor means extends through thetunnel and beyond the input and output openings on one or both sides,the machine further comprising: a plurality of tunnel wall panelsfoldably attached to the X-ray tunnel at one or both of the input andoutput openings.
 51. An X-ray security inspection machine, comprising:an X-ray tunnel for receiving an article to be inspected; a conveyormeans for conveying the article through the tunnel; an X-ray source forirradiating the article within the tunnel; and an X-ray detection meansfor detecting X-rays transmitted through the article, the X-raydetection means comprising: a first unit having a first photodetectorarray; and a second unit having a second photodetector array and beingoffset with respect to the first unit, wherein the first and secondunits are moveable relative to one another between a first arrangementin which the first and second photodetector arrays overlap to a firstdegree and a second arrangement in which the first and secondphotodetector arrays overlap to a second, lower degree.
 52. The X-raysecurity inspection machine of claim 51, wherein the second degree iszero.
 53. A conveyor belt-tracking device for tracking a conveyor beltof an X-ray security inspection machine in a straight line, the devicecomprising a guide frame arranged to receive the conveyor belt andsubstantially to restrict motion of the conveyor belt to a predetermineddirection.
 54. The device of claim 53, the guide frame comprising upperand lower runner portions arranged to receive the conveyor belt therebetween and substantially to prevent motion of the conveyor belt in adirection normal to the predetermined direction.
 55. A conveyor systemfor an X-ray security inspection machine comprising a conveyor belt anda respective conveyor belt-tracking device of claim 53 disposed onopposite sides of the conveyor belt.
 56. An X-ray security inspectionmachine, comprising: an X-ray tunnel for receiving an article to beinspected; a conveyor means for conveying the article through thetunnel; an X-ray source for irradiating the article within the tunnel;and an X-ray detection means for detecting X-rays transmitted throughthe article, wherein the X-ray detection means comprises a photodetectorarray module actuatable between a first stowed configuration and asecond deployed configuration, further comprising the conveyorbelt-tracking device of claim
 53. 57. An X-ray security inspectionmachine, comprising: an X-ray tunnel for receiving an article to beinspected; a conveyor means for conveying the article through thetunnel; an X-ray source for irradiating the article within the tunnel;and an X-ray detection means for detecting X-rays transmitted throughthe article, wherein the X-ray detection means comprises a photodetectorarray module actuatable between a first stowed configuration and asecond deployed configuration, further comprising the conveyor system ofclaim 55.